A zoom lens system is generally comprised of multiple zooming lens groups wherein all groups must be kept aligned on the optical axis of the zoom lens system. That is to say, the lens groups must be aligned concentrically on the optical axis of the system. For zooming action each group must be independently translatable along the optical axis according to lens zoom cam data while being constrained against off-axis displacement; both laterally, in a plane orthogonal to the optical axis, as well as rotationally, through an angle deviating from the direction of the optical axis.
Zoom lens mounts using multiple sleeved barrels with pins in cam slots are well known for providing the desired constrained motion. Such zoom lens drive mechanisms are known to have problems however. For instance, in order to minimize loss of constraint on the zoom lens drive mechanism, very tight part tolerances are required on the lens barrel, the axial groove in the lens barrel, the driving pin, the cam barrel, the cam groove, and the lens subgroup. Without tight tolerances, the lens subgroup is subject to tilting or lateral deflection within the lens barrel upon application of the driving force provided by the driving pin and cam barrel. Deflection or tilting of the lens subgroup within the lens barrel is undesirable since the optical axis of the subgroup would likewise be deflected from the optical axis of the lens barrel.
It would thus be desirable to provide a zoom lens drive mechanism that reduces the need for tight tolerances on the majority of parts making up the zoom lens drive mechanism. Preferably, such a drive mechanism should minimize or eliminate the need for multiple sleeve arrangements thereby providing a more simplified and reliable zoom drive mechanism.